In a wide variety of industries, including the food processing, chemical and mineral processing industries, fluids are conveyed via pipelines between stages within an industrial plant or process, or between the plant and end users. At every point where one pipe joins another pipe, there is a flange connection to permit the pipes to be joined together, typically by bolts and nuts and sometimes by welding. Each flange connection requires a sealing system to ensure a fluid-tight seal is maintained between the flanges. A common prior art sealing system is the spiral-wound gasket.
Spiral-wound gaskets are formed from a metal strip, typically stainless steel, which is wound together with a filler material such as graphite, TEFLON (Registered Trade Mark), treated asbestos fibre, etc, to form a core. A constant tensile force is applied during the winding process to give the core an inherent recovery force or resilience under compressive load. Both supported and unsupported spiral-wound gaskets are common. A supported spiral-wound gasket is provided with a solid outer metal ring which is used as a centering and compression control device. To further enhance the pressure rating of the gasket a solid metal inner ring may also be provided.
There are many other types of gaskets and flange sealing systems apart from spiral-wound gaskets. However there is a common problem with these prior art sealing systems. Each gasket or flange sealing system must be manufactured to fit or comply with the particular pressure class and/or flange standard applicable to the pipeline concerned. There are a number of international flange standards employed including British Standard (BS), American National Standards Institute (ANSI), Japanese International Standards (JIS) and Deutsches Institut für Normung (DIN). This has resulted in a proliferation of products designed to fit each of the international flange standards, as well as the numerous pressure ratings of various pipelines. Therefore in order to provide adequate service and maintenance of pipelines it is necessary for companies to hold a huge inventory of spare gaskets and sealing systems in stock. This adds considerably to the cost of maintenance and as well as warehousing costs.
When using a centering ring to locate a sealing element relative to two pipe end flanges fastened together, prior art configurations teach that the ring must be mounted to fully and continuously surround the sealing element to provide sufficient support to the sealing element. One example of continuous support about the circumference of a Sealing Gasket is described in British Patent 1,017,294 by Quinson.
U.S. Pat. No. 1,896,795 by Kendall discloses a further example of a sealing element supported by a centering ring. In this instance, the centering ring is initially formed to be discontinuous to allow flexing when the sealing element is inserted therein. Kendall teaches that the ends of the discontinuous ring must be joined together by lugs prior to placement in a mounted position between the end flanges in order to provide sufficient support to maintain the centering ring in position about the sealing element in use. Once the ends of the centering ring are joined, the sealing element can no longer be readily removed so that the centering ring and sealing element are discarded together once the sealing element is no longer in suitable condition for sealing.
Veiga, U.S. Pat. No. 6,994,356, discloses another example of a sealing element supported by a surrounding centering ring. The centering ring is formed from two semi-circular sections which are joined about the sealing element by welding the ends together. Similarly to Kendall noted above, once the sections of the centering ring are joined about the sealing element, the sealing element can no longer be readily removed so that the centering ring and sealing element are discarded together once the sealing element is no longer in suitable condition for sealing.
U.S. Pat. No. 1,892,416 by Ruhe et al. discloses a sealing member for flanged joints which requires a centering collar to be provided about which the sealing element is supported. An outer support ring is provided to maintain support of the sealing element about the inner centering collar. The outer support ring is discontinuous and is flexible to allow removal and replacement of the sealing element. In order to adequately support the sealing element, Ruhe et al. teaches that the sealing element must be mounted about the inner collar and that a spring must be connected between the disconnected ends of the outer support ring prior to placement in the mounted position. The spring construction is awkward to install and to maintain so that the resulting sealing member is costly and has a life which is limited by the spring used to maintain the tension of the outer ring about the sealing element.
References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.